The present invention relates to a supply head of a nut feeder where a welding nut is supplied to prescribed welding position of a work.
In the prior art, such a supply head disclosed in Japanese Utility Model Publication No. 56-14943/1981 shown in FIG. 1 is known.
The supply head 1 is provided at the front end of the supply head body 2 with a sleeve 3 where a welding nut 80 transferred through a chute 9 is received in the inside of the front end. Within the sleeve 3 is arranged a rod 6 which is capable of being moved forwar and backward in the axial direction of the sleeve 3 and provided at the front end surface with a holding surface 6a capable of attracting the end surface of the welding nut 80 transferred into the sleeve 3 during the forward motion after magnetization for prescribed time and with a projection 6b inserted in a tapped hole 80a at the center. A shutter 8 being opened or closed freely so as to block the front side of the transferred welding nut 80 is arranged at the front end of the sleeve 3. On the lower surface of the front end of the rod 6 is fixed a guide rod 7 guiding a welding nut circumferential surface 80b when the transferred welding nut 80 is disposed at the prescribed welding position of a work 60. Numeral 4 designates a coil to magnetize the rod 6 for prescribed time, and numeral 5 designates a stopper where the welding nut 80 transferred through the chute 9 is stopped within the sleeve 3.
The supply head 1 is operated as follows.
First, the welding nut 80 is transferred through the chute 9 to the inside of the front end of the sleeve 3 from the upper side.
The rod 6 is magnetized and moved forward. In this case, the projection 6b of the rod 6 is inserted in the tapped hole 80a of the welding nut 80 and the holding surface 6a of the rod 6 attracts the end surface of the welding nut 80, and the welding nut 80 opens the shutter 8 and is separated together with the front end of the rod 6 from the sleeve 3.
When the front end of the rod 6 is advanced to the welding position of the work 60, a part of the lower edge of the welding nut 80 abuts on the upper surface of the work 60. In this case, since the rod 6 is demagnetized and the attracting force is released, the welding nut 80 is rotated about the abutting position with the work 60 as a fulcrum and the circumferential surface 80b is guided by the guide rod 7 at the front end of the rod 6, thereby the welding nut 80 is fitted to a guide pin l0a of a lower electrode 10 of a welder and is arranged in the prescribed direction to the prescribed welding position of the work 60.
And then the rod 6 is moved backward and returned to the origianl position, and next welding nut 80 is supplied in similar manner.
When a part of the lower edge of the welding nut 80 abuts on the upper surface of the work 60 and the welding nut 80 is rotated and arranged to the prescribed position of the work 60, the supply head 1 utilizes the guide rod 7 at the front end of the rod 6 guiding the circumferential surface 80b of the welding nut 80 and guides the arranging direction of the welding nut 80.
Consequently, the supply head 1 can direct the transferred welding nut 80 to the prescribed direction and arrange it in the work 60, thereby the welding nut 80 of quadrilateral, hexagon or the like can be supplied stably.
In the supply head 1 in the prior art, however, when a T-shaped welding nut (hereinafter referred to as "T-nut") 90 as shown in FIGS. 10-12 is supplied, it cannot be supplied stably in some case. This occurs, for example, in the case that the T-nut 90 is supplied to a narrow portion of a work 70 as shown in FIGS. 10, 11. The T-nut 90 is provided with a tapped portion 91 and a flange portion 92, where the tapped portion 91 is of cylindrical shape, and the flange portion 92 is of rectangular plate shape and both end surfaces 92a, 92b in major axis direction are convexly curved arcuate surfaces and both end surfaces 92c, 92d in minor axis direction are made planes in parallel to each other.
In order to supply the T-nut 90 to the work 70 utilizing the supply head 1, a problem occurs first in that the projection 6b of the rod cannot be inserted in the tapped hole 91a of the nut.
That is, in such a T-nut 90, since the flange portion 92 is forged in disk shape at first by a press or the like and then both end surfaces 92c, 92d in minor axis direction are only formed by cutting work, it is inevitable that length of the flange portion 92 in major axis direction and arrangement of the tapped portion 91 of the flange portion 92 in major axis direction become uneven. Consequently, when the T-nut 90 transferred through the chute 9 from the upper side in the state of the major axis direction of the flange portion 92 being made nearly the vertical direction is stopped by the stopper 5 in the abutting state of the end surface 92a of the flange portion 92, the arrangement cannot be performed in some case so that the tapped hole 9la of the T-nut is always coincident with the front side of the projection 6b of the rod.
Even if the attraction to the rod 6 is performed properly, when the T-nut 90 is inserted between side walls 71, 71 of the work from the X-direction, the T-nut 90 cannot be inserted in some case.
That is, the T-nut 90 is attracted and moved in the state that the major axis direction of the flange portion 92 is arranged in nearly the vertical direction with respect to the rod 6, but since dimension L of the flange portion 92 in major axis direction is longer than dimension S in minor axis direction and the major axis direction of the flange portion 92 is arranged in nearly the vertical direction, the rotation moment about the tapped portion 91 being the center is liable to act. Consequently, the flange portion 92 is liable to be rotated in the attracted state to the holding surface 6a of the rod by vibration or the like. When the T-nut 90 has been rotated, during inserting between the work side walls 71, 71, the flange portion 92 abuts on the side walls 71, 71 and the T-nut 90 is detached from the rod 6 in some case.
Further, even if the inserting is performed between the work side walls 71, 71 properly, when the tapped portion 91 is fitted to the guide pin l0a of the prescribed lower electrode, the tapped portion 91 cannot be fitted to the guide pin l0a in some case.
That is, during the arrangement to the upper surface of the work 70, the lower edge of the end surface 92a in the major axis direction of the flange portion abuts on the upper surface of the work 70 and the T-nut 90 is rotated and arranged about the abutting portion as a fulcrum. In this case, since the end surface 92a being the fulcrum portion is made as a arcuate surface, the rotation moment about the tapped portion 91 being the center also acts on the T-nut 90. Consequently, the unnecessary rotation is applied to the T-nut 90, and the tapped portion 91 cannot be fitted to the guide pin l0a of the lower electrode in some case.